One-piece yoke thrust bearing for a piston and connecting rod assembly and method utilizing said bearing

ABSTRACT

A method of assembling a piston, connecting rod, wrist pin, and yoke thrust bearing is disclosed wherein the method comprises the steps of disposing between the piston and connecting rod, a one-piece yoke thrust bearing thereby providing a bearing surface between a wrist pin boss and the connecting rod. The piston includes a pair of wrist pin bosses disposed therein and in spaced-apart facing relationship. The bosses have oppositely disposed faces with axially aligned bores therein, and the faces have disposed therein respective shoulder-like depressions. The yoke thrust bearing comprises a pair of washer portions in abutment against respective boss faces and interconnected by a yoke element, and the washer portions have respective projections conformably received in respective depressions, thereby aligning the holes in the washers with the bores and preventing rotation of the yoke thrust bearing in the piston. One end of the connecting rod is received between the washer portions, and a wrist pin is passed through the boss bores, washer portions, and the connecting rod opening to thereby pivotally connect the piston and connecting rod together.

This is a division of application Ser. No. 560,531, filed Dec. 12, 1983.

BACKGROUND OF THE INVENTION

This invention pertains to a piston and connecting rod assembly, andmore particularly to an improved piston and connecting rod assembly forcompressors and internal combustion engines, such as small two and fourcycle engines, for example. A one-piece yoke thrust bearing is disposedbetween the piston and connecting rod to provide bearing surfacestherebetween.

In many engines, the connecting rod is guided either by shoulders on thecrankshaft or by wrist pin bosses in the piston. Copending applicationSer. No. 437,363 filed Oct. 25, 1982 discloses a prior art crankshaftand connecting rod assembly wherein the connecting rod is not guided onthe crankshaft, and suitable bearings within the piston must beprovided.

Current pistons for guiding the connecting rod in the piston generallycomprise a pair of wrist pin bosses, wherein the bosses have oppositelydisposed and spaced-apart faces, which have a smooth hard finish, and apair of bores disposed through the respective bosses. One end of aconnecting rod having an opening therethrough is disposed between theboss faces, and a washer is positioned between each face and one side ofthe connecting rod to provide bearing surfaces therebetween. A wrist pinis then passed through the boss bores, the two washers, and the openingin the connecting rod.

In assembling the above type piston and connecting rod assembly, one ofthe major difficulties is passing the wrist pin through the bores, bothwashers, and the connecting rod opening without displacing one of thewashers out of axial alignment or dropping one of the washers out of thepiston. This assembly is also quite time consuming since it requires theassembler to first align one of the washers with a bore, pass the wristpin through the bore and through the washer, then insert the connectingrod and pass the pin through the connecting rod opening, and then alignthe second washer between the connecting rod and the other bore so thatthe wrist pin may then be passed therethrough. Clearly, multiplerepetitions of this manual method of assembling will increase thelikelihood of washers becoming displaced, dropped out of the piston, orpossibly result in the assembling of the piston and connecting rod withonly one washer.

Although the use of a stacking pin eliminates the necessity ofindividually aligning the washers and connecting rod with the wrist pin,it nevertheless is time consuming in that the operator must handle threeitems, i.e., two washers and the connecting rod, in assembling thepiston and connecting rod together.

Further, most currently used washers are made of hardened and groundsteel, and are therefore individually quite costly, and increase theoverall cost of the engine.

SUMMARY OF THE INVENTION

The present invention overcomes the problems and disadvantages of theprior art by providing an improved piston and connecting rod assemblywherein a one-piece yoke thrust bearing is disposed between the bossfaces and the connecting rod. The assembly of the present invention inone form thereof provides on the boss faces respective shoulder-likenotches or depressions, and includes a one-piece yoke thrust bearingcomprising a pair of washer portions interconnected by a yoke element.The washer portions have complementary shaped projections, which arereceived in respective depressions, thereby guiding the thrust bearingin place, providing self-alignment of the washer holes with the boresand preventing rotation of the yoke thrust bearing within the piston.Compared to assembling the two individual washers of the prior artassembly, the one-piece yoke thrust bearing can be easily and quicklyinstalled in the piston, either manually or automatically, therebyproviding a saving in time and expense.

Further, the one-piece yoke thrust bearing is made of partially hardenedspring steel, and is therefore inexpensive compared to the two groundand hardened washers of current piston and connecting rod assemblies,thereby providing a further savings in cost.

The ends of the wrist pin are preferably rounded or chamfered to assistin aligning the holes.

In one form of the invention there is provided a piston and connectingrod assembly comprising a piston having a pair of wrist pin bosses,which have respective faces in spaced-apart and facing relationship witheach other, and respective bores in axial alignment. One end of theconnecting rod, which has an opening therein, is disposed between thefaces so that the opening is in axial alignment with bores. A one-piecebearing member has a pair of washer portions respectively disposedbetween the faces and the connecting rod end, and a yoke portion extendsaround the connecting rod one end and interconnects the washer portions.

The present invention also provides a method of assembling a piston andconnecting rod, which has an opening in one end thereof, comprising thesteps of providing a piston including a pair of wrist pin bosses havingrespective faces in spaced-apart and facing relationship with eachother, the bosses having respective bores in axial alignment therein,and further providing a one-piece bearing member comprising a pair ofwashers interconnected by a yoke element, wherein the washers haverespective holes in axial alignment with one another. The washers of thebearing member are inserted between the boss faces, and the holes in thewashers are aligned with the bores in the boss faces. Then, the one endof the connecting rod is positioned between the washers, and the openingin the one end is aligned with the boss bores and washer holes.Thereafter, a wrist pin is passed through the aligned bores, holes, andopening.

It is an object of the present invention to provide an improved pistonand connecting rod assembly.

Another object of the present invention is to provide a one-piece yokethrust bearing disposed between the piston and connecting rod forproviding bearing surfaces therebetween.

Yet another object of the present invention is to provide a piston andconnecting rod assembly which is less expensive to manufacture thanprior assemblies.

A further object of the present invention is to provide an improvedmethod of assembling a piston and connecting rod together.

Yet still another further object of the present invention is to providea method for easily and quickly assembling a piston and connecting rodtogether.

Further objects of the present invention will appear as the descriptionproceeds.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-mentioned and other features and objects of this invention,and the manner of attaining them, will become more apparent and theinvention itself will be better understood by reference to the followingdescription of an embodiment of the invention taken in conjunction withthe accompanying drawings, wherein:

FIG. 1 is a perspective view of a preferred embodiment of the presentinvention connected to a crankshaft;

FIG. 2 is an exploded view of the embodiment of the present invention inFIG. 1;

FIG. 3 is a front elevational view of the yoke thrust bearing of theembodiment;

FIG. 4 is a bottom plan view of the yoke thrust bearing with the washerportions in the deflected position;

FIG. 5 is a side elevational view of the yoke thrust bearing;

FIG. 6 is a bottom plan view of the piston of the embodiment;

FIG. 7 is a sectional view of FIG. 6 taken along line 7--7 and viewed inthe direction of the arrows;

FIG. 8 is a bottom plan view of the piston with the yoke thrust bearinginserted therein;

FIG. 9 is similar to FIG. 8 with the connecting rod inserted in the yokethrust bearing and the wrist pin slightly spaced-apart from the piston;and

FIG. 10 is a sectional view of the assembled embodiment of the presentinvention.

DESCRIPTION OF A PREFERRED EMBODIMENT

Referring to FIG. 1, piston and connecting rod assembly 20 of thepresent invention is illustrated with crankshaft 22 connected thereto.Piston and connecting rod assembly 20 generally comprises connecting rod24, piston 26, one-piece yoke thrust bearing 28, and wrist pin 30 (FIG.2).

Referring to FIGS. 1, 2, 6, and 7, piston 26 has a head 23, a skirt 25with an inner surface 32 having a pair of wrist pin bosses 34,36oppositely disposed thereon and having respective faces 38,40 inspaced-apart and facing relationship. Boss 34 has bore 42 therein andboss 36 has bore 44 therein, the bores 42,44 being in axial alignmentwith each other. Bosses 34,36 further include two shoulder-like slots ordepressions 46,48 respectively disposed in faces 38,40. Depressions46,48 are disposed in the remote end portions of respective faces 38,40nearest opening 50 of piston 26 and extend to edges 47 (FIG. 7) ofbosses 34 and 36 that face away from piston head 23.

Referring now to FIGS. 1, 2, and 10, connecting rod 24 has opening 56 inone end thereof with steel sleeve 58 secured therein, and is rotatablysupported on bearing assembly 60 circumferentially disposed aboutcrankshaft portion 62 between shoulders 59 and adjacent counterweight64.

The opposite end of connecting rod 24 includes opening 66 with rollerand sleeve bearing 68 disposed therein.

Referring to FIGS. 1-5, yoke thrust bearing 28 comprises a pair ofspaced-apart washer portions 70,72 interconnected by yoke portion 74.Washer portions 70,72 have outwardly facing respective holes 76,78disposed therein and in axial alignment. The remote ends of washerportions 70,72 have respective projections 80,82 disposed on theiroutwardly facing surfaces 84,86, respectively. Projections 80,82 areformed to be complementary to depressions 46, 48 in faces 38,40.

Yoke portion 74 comprises midportion 88 and two wider end portions 90,92on opposite sides of midportion 88. Yoke portion 74 is preferablyintegrally joined to washer portions 70,72 at respective junctures94,96.

As illustrated in FIG. 3, washer portion 70 includes a top segment 98and a bottom segment 100, through which hole 76 is disposed. Segments98,100 are outwardly disposed angularly from yoke element 74, andsegments 98,100 are joined together at 102 such that bottom segment 100is spaced outwardly from top segment 98, both segments 98 and 100 lyingin parallel planes.

In an identical manner, washer portion 72 includes top segment 104 andbottom segment 106 at 108, and segments 104,106 are outwardly disposedangularly in parallel planes from yoke element 74. It should be notedthat FIG. 3 illustrates yoke thrust bearing 28 in a free state, i.e.,washer portions 70,72 are in their normal state diverging from yokeelement 74 In contrast, FIG. 4 illustrates yoke thrust bearing 28 in itsinwardly deflected state when positioned between boss faces 38,40, aswill be explained in detail below.

FIGS. 2, 9, and 10 illustrate wrist pin 30 which is received throughbores 42,44; holes 76,78; and opening 66. Wrist pin 30 is cylindrical inshape and has opposite ends 110, 112 having respective peripheries114,116. To assist in passing wrist pin 30 through bores 42,44, holes76,78, and opening 66, peripheries 114, 116 are shaped with chamferedsurfaces or rounded surfaces to assist in assembly.

The method of easily and quickly assembling piston 26 and connecting rod24 is illustrated primarily in FIGS. 2, 8, 9, and 10. FIG. 2 illustratespiston and connecting rod assembly 20 before assembly and includesconnecting rod 24, piston 26, yoke thrust bearing 28, and wrist pin 30.The assembling of piston and connecting rod assembly 20 comprisesinserting yoke thrust bearing 28 between bosses 34,36 by positioningyoke element 74 therebetween and deflecting washer portions 70, 72inwardly to permit them to slide against faces 38,40 until projections80,82 are received in respective depressions 46,48. Depressions 46,48are located in faces 38,40 such that holes 76,78 are in axial alignmentwith respective bores 42,44 when projections 80,82 are conformablyreceived in depressions 46,48, respectively. Thus, depressions 46,48 andprojections 80,82 serve to axially align holes 76,78 with bores 42,44,and further serve to lock yoke thrust bearing 28 against rotation.Further, surfaces 84,86 of respective washer portions 70,72 abut againstrespective faces 38,40, thereby providing bearing surfaces betweenbosses 34,36 and connecting rod 24.

FIG. 8 illustrates yoke thrust bearing 28 assembled in piston 26 in itsinwardly deflected state. Referring now to FIG. 9, connecting rod 24 isthen positioned between washer portions 70,72, and opening 66 is alignedwith holes 76,78 and bores 42,44. Thereafter, wrist pin 30 is passedthrough bores, 42,44, holes 76,78, and opening 66, as illustrated inFIG. 10. A snap retainer 87 and shoulder 89 retain pin 30 in piston 26.

FIG. 10 further illustrates yoke element 74 spaced-apart from andintermediate connecting rod 24 and bottom surface 118 of piston 26.Further, a certain amount of tolerance is present between yoke thrustbearing 28 and connecting rod 24.

Yoke thrust bearing 28 is preferably made of 0.0285 to 0.0315 thickpartially hardened spring steel of Bainite structure with a Rockwell Chardness of about 27 to 36, and has a scaleless tempered finish.

While this invention has been described in terms of a preferredembodiment, it will be understood that it is capable of furthermodifications. This application is therefore intended to cover anyvariations, uses, or adaptations of the invention following the generalprinciples thereof, and including such departures from the presentdisclosure as come within known or customary practice in the art towhich this invention pertains and fall within the limits of the appendedclaims.

What is claimed is:
 1. A method of pivotally assembling together apiston and a connecting rod having an opening in one end thereof,comprising the steps of:providing a piston including a pair of wrist pinbosses having respective faces in spaced-apart and facing relationshipwith each other, the bosses having respective bores in axial alignment,providing a one-piece bearing device comprising a pair of washersinterconnected by a yoke element, the washers having axially alignedholes therein, inserting the washers of the one-piece bearing devicebetween the boss faces, aligning the holes in the washers with the boresin the boss faces, then positioning the one end of the connecting rodbetween the washers, aligning the opening in the one end with thealigned boss bores and washer holes, and thereafter passing a wrist pinthrough the aligned bores, holes, and opening.
 2. The method of claim 1wherein the washers are resiliently biased outwardly relative to theyoke element, and the step of inserting the washers includes deflectingthe resiliently biased washers inwardly by the piston bosses as thebearing device is inserted in the piston.
 3. The method of claim 1wherein the piston includes a pair of locking elements on the respectivefaces, the one-piece bearing member includes a pair of engaging elementson the respective washers, and the step of inserting the washersincludes lockingly engaging the locking elements with the respectiveengaging elements, thereby preventing rotation of the bearing device. 4.The method of claim 1 wherein the boss faces include open slots therein,the washers include outwardly facing projections, and the projectionsare guided in the grooves as the bearing device is inserted in thepiston.